170 Vol. 4 VEGETATIVE PROPAGATION ROOTING PRACTICES WITH FOREST TREES IN INDIA H. P. BHATNAGAR Forest Research Institute, Dehra Dun, India (Received for publication 13 September 1973) ABSTRACT Plantations of most of the economically important forest species in India are usually established with seedlings, either by entire transplanting of nursery stock or by stump planting. Willows (Salix spp.) and poplars (Populus spp.) are the only forest trees which are widely planted as shoot cuttings. However, rooting of cuttings is also practised to propagate, on a small scale, Bursera penicillata (Sesse et Moc. ex D.C.) Engl., Morus alba L. and a few other forest tree species. Bamboos, which are an important forest component, are widely propagated by vegetative means. With forestry becoming more intensive the interest in vegetative propagation has increased. This has prompted laboratory and field studies, to improve existing techniques, and to extend vegetative propagation to other species, e.g., teak (Tectona grandis L.f.). This paper out­ lines methods already in use, and reviews the research on vegetative propagation which has been done at Dehra Dun and elsewhere in India. INTRODUCTION In the present-day context of intensive management of forest land, with the intro­ duction of fast-growing exotics and genetic improvement of forest tree species, it is most important to develop fast and economical methods of raising superior stock. Vegetative propagation of forest trees is potentially very useful for replicating clonal material and for the multiplication of stock. Clones offer the advantages of genetic uniformity and the immediate availability of superior individuals for seed orchards and for plantations. Considerable efforts have been made in many countries to develop techniques of clonal propagation for tree improvement programmes and for field afforestation. Of various methods of vegetative propagation of forest tree species, the one most likely to succeed on a large scale is the rooting of shoot cuttings. Setting of cuttings can avoid the problems of seed collection and of ensuring germination and subsequent survival of young seedlings. Stem or shoot portions are generally very good material for rooting purposes, because they usually have undifferentiated tissues which may permit initiation of root primordia, and they also have buds already formed. The frequent early flowering of shoot cuttings can save time and makes the work of the tree breeder easier as he can work much closer to the ground. There are numerous reports on the raising of shoot cuttings, e.g., Yin & Liu, 1948; Fielding, 1954; Ohmasa, 1956; Nienstaedt et al, 1958; Schrieber, 1963; Thulin & N.Z. J. For. Sci. 4 (2): 170-6 No. 2 Bhatnagar — Vegetative Propagation Rooting Practices 171 Faulds, 1968; McKnight, 1970; Hill & Libby, 1970. Poplars (Populus spp.), for example, are established in many countries mainly as shoot cuttings, and so is Cryptomeria japonica (L.f) Don, a valuable timber species in Japan. Various studies aimed at improving rooting techniques with forest tree species have involved the physiology of rooting, with particular reference to auxins and nutritional relationships (Snow, 1941; Mirov, 1944; Thimann & Behnke, 1947; Yim, 1962; Matthews et al, I960; Fielding, 1964; Libby, 1964; Bhatnagar et al, 1968 & 1972; Nanda et al, 1968 & 1970). TREE ROOTING PRACTICES Plantations of most of the economically important forest species in India are usually raised by entire transplanting of nursery-grown seedlings or by stump planting (i.e., using seedlings whose roots and shoots have been severely trimmed). However, in current practice in India, propagation of planting stock by cuttings is mainly used for establishing poplars and willows (Populus and Salix spp.). On a small scale shoot cuttings are also used to propagate Bursera penicillata (Sesse et Moc. ex DC). Engl. (Syn. Bursera delpechiana Poiss. ex Engl.) and Morus alba L. and occasionally Platanus orientalis L., Tamarix spp. and Ficus spp. Bamboos, although they are not really trees, are of great economic importance in Indian forestry; several species are raised by rooting planting stock by vegetative means. Poplars In recent years poplars have been increasingly cultivated. This genus is particularly evident in the Kashmir Valley and generally thrives between 1200 to 3050 m elevation. It becomes progressively less common towards the eastern Himalayas with increasing rainfall. Out of six species used, either indigenous or introduced. Populus euphratica Olivier and P. ciliata Wall, ex Royle are the most important (Seth & Desarkar, I960). However, since 1958, over 180 species and hybrids have been introduced by the Forest Research Institute, then multiplied, and finally released for trials throughout India. More promising clones are Populus "casale 488", P. "casale 15", P. "casale 214", P. "casale 438", P. "casale 30", P. robusta Schneid., P. regenerata 410, and, more particularly, Populus deltoides (IC, and other clones) for the plains and P. yunnanensis Dode for the hills (Seth, 1969; Pande, 1973). Propagation by stem cuttings is the standard procedure (Champion & Seth, 1968). Cuttings of about 20-25 cm or longer are taken from the terminal shoots of main upper branches of the trees or from the specially raised stool beds. Branch cuttings also have given good results. The best period for taking cuttings is between November and March (Seth & Desarkar, I960; Mathur, 1972). Cuttings are inserted vertically for their whole length in properly well-prepared nursery beds, preferably in sandy loam or sand with a high water table, at a spacing of 22 X 44 cm. Multiple shoots are reduced to one at an early stage. In the second year the shoots 'are cut back about 2 cm above the ground level and replanted in good soil at 40-60 cm spacing. By the end of the year they are ready for out-planting in the field. With hybrid poplars, longer cuttings of about 50 cm have given superior height growth. Willows Vegetative propagation is the standard practice with willows (Salix spp.). S. tetrasperma Roxb. is the most common Indian willow and it occurs between 1800 and 2200 m elevation. About five introduced species of willow are widely planted in India, 172 New Zealand Journal of Forestry Science Vol. 4 of these S. alba L. var. caerulea Sm. is commonly cultivated, mainly in Kashmir Valley, for the manufacture of cricket bats (Troup, 1921; Kaushik, 1961). Propagation is generally carried out by planting sets or shoot cuttings of various sizes from January to March, depending on the local weather. Shoot cuttings of 90 to 120 cm length and 3 to 5 cm thick are taken from healthy branches of mature trees and are cut obliquely at each end. They are planted in nursery beds, with a spacing of 90 X 60 cm. The cuttings are set 60 to 90 cm deep in the soil (Keng, 1957). More recently, to minimise the curve at the base of the shoot, a technique of raising the sets in the nursery is being practised. The shoots are grown into sets of 5 to 8 cm diameter at the lower end with a height of about 2.5 to 3 metres. Often, willows are used in irrigated plantations. Regular irrigated channels of about 0.3 X 2 m cross section are prepared at the planting site 6 to 4.5 m apart. Sets are planted in February-March in 40 to 60 cm-deep pits in the prepared channels in a triangular pattern (Kaushik, 1961). Bursera Bursera penicillata (Sesse et Moc. ex D.C.) Engl, is a small bushy tree introduced from Mexico. The species yields an aromatic essential oil used in soap and perfume production. Every part of the tree contains oil, the maximum concentration being in the pericarp of the fruit (Shyam Sunder, 1972). The species can be propagated both by seed and by branch cuttings. Propagation by branch cuttings is the easiest way for the multiplication of the species. Cuttings of 5 to 8 cm diameter and about 45 cm long are taken during the month of March just before the new leaves appear. The cuttings are generally hung vertically for a day to drain excess oil. Cuttings with one or two* side' branches on the top giwe good growth, and shown better crown formation than straight cuttings without branches. The lower end of the cutting is treated with Seradix B. Such cuttings are planted in pots filled with equal parts of soil and farmyard manure. Profuse watering is done for a few days. The cuttings take 10-15 days to root. Planting in the field is done soon after the monsoon begins (generally during July) in 60-90 cm cubical pits at a spacing of 7 X 7m. A mixture of manure, soil and sand is used for filling the pits. Cuttings from male and female plants are planted in the ratio of 1:9 (Kaikini, 1968; Rao, 1971). Mulberry Of six species of mulberry which occur in India Morus alba L. is the most widely cultivated. It is a moderate-sized deciduous tree having many distinct varieties, or cultivars. The wood is used mainly for making hockey sticks, furniture, etc. This is the species of Morus which is used most for silkworm rearing in India (Troup, 1921). The tree is very easily propagated, either from seed or from cuttings. Branch cuttings about 22-30 cm long and 2 cm thick having 2-3 buds on them are taken from mature trees for rooting in the nursery. In some areas the usual practice is to bundle the cuttings and bury them under the soil, watering regularly until the buds sprout and produce a shoot about 5 cm long. Such sprouted cuttings are taken out for planting in pits or in furrows. Pit planting is preferred and is practised both in irrigated and dry cultivation areas. In dry cultivation areas cuttings are planted completely buried in prepared pits, in a slanting position, at the onset of the monsoon.